Giant longitudinal and transverse magnetothermoelectric effects in a van del Waals semimetal TaCo2Te2

Abstract

Nowadays, thermoelectric (TE) cooling technologies are hindered by the paucity of efficient low-temperature TE materials, which are critical to both cryogenic research and practical applications. Herein, we present the discovery of a flexible van der Waals semimetal TaCo₂Te₂, which exhibits exceptional TE performance in both the longitudinal and transverse directions. The transverse power factor reaches an unsaturated ultrahigh value, 25 680 μW m⁻¹ K⁻², under 13.5 T at 20 K, surpassing the performance of most transverse TE materials. Two longitudinal power factor peaks are observed, dominated by different carriers, with the highest recorded values of 11 600 μW m⁻¹ K⁻² at 20 K in the electron-dominant region and 2200 μW m⁻¹ K⁻² at 120 K in the hole-dominant region without magnetic field. This outstanding TE performance can be attributed to high mobility and the phonon drag effect, underscoring TaCo₂Te₂ as a promising material candidate for low-temperature solid-state cooling applications within TE technology.